The present invention relates to a high-performance internal-combustion engine, particularly of the four-stroke type.
As is known, in internal-combustion engines combustion is produced by the ignition of the air-fuel mixture by means of the spark produced by the spark plugs. In order to obtain good combustion and a significant reduction in the volume of the exhaust gases and unburnt gases, the modern technology used in high-performance engines relies on the use of sophisticated electronic equipment, such as for example centralized units for controlling ignition and adjusting the flow of fuel into the combustion chamber, in order to achieve optimum filling of the cylinders.
The flow of fuel into the combustion chamber is generally adjusted by means of injection systems which can be divided into three main types: fuel injection with a mechanical method, electronic injection, and finally mechanical injection with electronic adjustment.
In mechanical injection devices, the fuel is injected into the induction manifold with the same method used for injecting Diesel fuel in Diesel-cycle engines. The injector is a passive valve that opens spontaneously when the fuel reaches it with a pressure higher than the value for which its spring is set. Accordingly, the feed circuit includes an electric pump which feeds the fuel at an adequate pressure and sends it to a distribution unit that distributes it simultaneously to all the injectors in an amount proportionate to the mass of air entering the cylinders. In this type of injection device, injection occurs continuously, with no reference to the position of the system. A mechanical injection system of the type described above is, for example, the device commercially known by the name K-Jetronic of the Bosch company, and is composed exclusively of metering units, regulators and metering units of a mechanical type. In particular, there is a rocker diaphragm that weighs the amount of air flowing through the manifold.
Differently from mechanical injection devices, electronic injection devices, such as for example the devices commercially known by the names IWA by the Magneti Marelli company or L-Jetronic by the Bosch company, have no moving mechanical parts, although at the base of the circuit there is an electric pump that feeds the fuel at lower pressures than those of mechanical-injection devices. The heart of the electronic system is constituted by the injector, which is no longer a passive valve but an active valve. In other words, it determines the moment of injection, the duration and the amount of fuel injected, by virtue of the fact that it is controlled electronically. The two electric wires powering it are in fact controlled by a control unit to which the various sensors for measuring air flow-rate, rpm rate, throttle position and engine temperature are connected. The injection can be a single one in the manifold (single-point injection) or on each inlet valve (multi-point injection), and can take into account the position of the piston. In this last case, the injection is also termed sequential or timed.
Mechanical injection devices with electronic adjustment, such as for example the device commercially known by the name KE-Jetronic by the Bosch company, are devices in which injection is mechanical but fuel metering and idling conditions are controlled by an electronic control unit connected to sensors.
Although they have helped to improve the performance of internal-combustion engines, the above described injection devices have shown some limitations in terms of cylinder filling and in terms of disproportion in the charge in the cylinders; overcoming these limitations would lead to an even better thermodynamic efficiency of internal-combustion engines.